Posted
by
CmdrTacoon Tuesday September 14, 2010 @08:03PM
from the yakkity-yak dept.

disco_tracy sent in a story about some fancy new power technology designed to tap energy from sound waves. Although the cell phone concept grabs the headline, they also talk about harvesting noise from traffic.

People who live near highways and main roads know how hard it is to get rid of traffic noise... if such a system catches 100% sound wave, that's a wave that dies at that point and is no longer heard. And, if that gets converted back to power, that's worth something in money.

Just remember Newton's Law of Energy Conservation... and remember that things powered by the car driving over a power capturing device is stealing gas from your tank indirectly.

...and remember that things powered by the car driving over a power capturing device is stealing gas from your tank indirectly.

Stealing? Are you trying to troll by attempting to get people outraged that the device powers from the sound generated due to inefficiency of your vehicle?

It is technically true, the energy of the sound does comes from your fuel tank. But remember that your car would still be expanding just as much energy on generating the noise whether or not there is any sound-gathering device around. Driving on the country road in the middle of nowhere will not increase your fuel efficiency.

Really the term "stealing" is completely invalid in this case. Now if the headline was about some fancy road surface that converted traction into energy then you would be absolutely correct, because it would adversely affect the performance of your vehicle, thus increasing its energy expenditure, thus stealing from your fuel tank.

Tell that to the people who demand to be compensated for their positive externalities [wikipedia.org] such as people who own patents, and people who pay (via tax/etc) for public services. None of these people like your argument because they bare all the cost, while others benefit from it.

Also, people who demand to be compensated for others negative externalities [wikipedia.org] such as people who live near a polluting factory, and people who want to protect the environment. None of these people like your argument because if the costs and

Who cares about 100%? If you can harvest a tiny fraction of energy that someone else is paying for, then you get that energy for free where it would otherwise go to waste.

Not to get too picky about it, but remember that the "tiny fraction" you harvest isn't "free". It needs to be worth at least enough to pay for the harvesting equipment, technology, deployment, maintenance, energy storage and transmission costs.

If we're talking about tearing up existing roads to install something and then also stoppin

He's complaining about the speed-bump-mounted pistons that some areas are using, which make your car do more work to generate power.

Of course, speed bumps in and of themselves end up causing more than an order of magnitude more deaths than they prevent thanks to their effect upon ambulances, so the power leeching is really only a drop in the bucket.

Since it would be using WASTE SOUND ENERGY, then no it's not 'stealing' gas. Let me know when the force a reduction i efficiency to support sound wave energy, then it will be indirectly costing you money,

In fact, and device that capturer waste energy in any form doesn't cost you a damn thing in the way of gas consumption.

In some case it can SAVE you money. Like using it on a ramp for care going down. It means less wear on brakes.

And just so you know, 20% reduction in sound from traffic is worth something...

Just make a phone that, while making a call, recharges its battery from the motion of the car. You've got a lot more energy to work with there than just sound energy, especially if you can derive energy from sudden stops.

That was my thought, too. And, unless my memory's wrong, there's not enough power involved for a cell phone. Of course, my familiarity with them is from almost forty years ago, so I wouldn't argue the point if anybody disagrees.

Yeah, any time an order is given over sound powered phones, the order is repeated back verbatim to ensure it was clearly heard, and it usually does go from an officer or chief through an enlisted person to another enlisted person.
The CO to the XO thing is not the norm since they the CO and XO are not together in Control during routine operations, but during a drill or emergency or some other special operation the CO might be at the conn, and the XO is the OOD (officer of the deck). You could then have the

This is a bogus story that wanders around every now and then. Cell phones require hundreds of milliwatts of transmit power, an amount of power far beyond what the human voice can achieve -- even at 100% conversion efficiency.

Presumably there would be a battery involved and the ambient noise would constantly charge the battery. I doubt anyone is claiming that you could just use one without a battery to talk for an infinite amount of time.

You're completely misunderstanding how it works. A. The human voice produces a hell of a lot more power than a cellphone, you can disagree if you want but it's not even relevant because: B. Ambient noise. It's not just you powering the device, it's everything that makes noise around you. and then, don't forget: C. Energy over time. It's charging it all day long, even when you're not on the phone. They aren't talking about you literally powering the phone as you talk. They are talking about a device on the p

The human voice produces a hell of a lot more power than a cellphone, you can disagree if you want

Well, a human shouting is about 1 mW. A cell phone's antenna outputs in the ballpark of 250 mW.

Some quick back-of-the-envelope calculations suggest that if the entire area of a cell phone could pick up sound energy, the ambient sound level was at the pain threshold of 120 dB (1 W/m^w), and it achieved 100% energy conversion, this would generate about 15 mW. For just the 250 mW antenna, this means about 90 minutes of talk time per 24 hours exposure.

120 dB is very loud, and a far cry from how much sound a phone would normally be exposed to. Note that sound is measured on a logarithmic scale. If the phone was constantly exposed to 60 dB of sound, then it'd only generate 15 nanowatts.

I was looking into this at one point and my numbers came up pretty much in line with Blueg3's. There just isn't enough power in sound to really provide significant mWh. No matter how advanced the collection technology if the power isn't there to start with you aren't going to get far.

Reduce, perhaps, but judging from the minimal amount of power available, you'd probably be better off throwing away the complex sound-harvesting technology and replacing it with a simple larger battery.

Not really. All of my estimates are very high (conversion of 100%, entire phone is covered in the sound-converting material, etc.), but the ambient noise level is the problem. In a crowded place like a restaurant, you're talking about maybe 60 dB of sound. An entire day's exposure to 60 dB of sound would get you less than 1 microwatt-hour. That's a uselessly tiny fraction of a battery's storage.

my chainsaw has 118dB @ 1m (it's a big one). Great, i don't need to charge my phone, just carry the battery-free sound-harvesting phone and a 7.3kg chainsaw, and gun that while i make a quick call to the ear clinic complaining about deafness.

Power is not measured in watts an hour. It's just watts. (Intensity is measured in W/m^2.)

0 dB (sound) is 10^-12 W/m^2. 60 dB is 10^-6 W/m^2. A 4 in. x 3 in. cell phone (with two sides) has an area of about 1.5 * 10^-2 m^2. So such an object subjected to 60 dB of background sound could capture up to 1.5 * 10^-8 W, which is 15 nW.

There is surprisingly little energy in sound. Take, for example, an object loud enough that the sound intensity at a distance of 10 m is 60 dB. The total sound energy output by that

People already keep their phones working 24x7. They also update their "status" telling the world of their whereabouts. More: many people already keep GPS tracking software like Latitude [google.com], constantly sending their coordinates to some third party's server.

I don't know who are "them", but "they" if they want to track most people, "they" don't need any tricks - people share that information voluntarily all the time.

"Sorry honey, you're about to cut out, just let me move closer to the traffic....hang on a sec, if I jump out in front of this car right here it'll honk and I'll get a power boost.....okay now that that's under control can you please talk a little louder? The traffic here in the middle of the highway is just shocking" *THUD*.

No thanks. Sounds like a bad idea. How efficient could the conversion be anyway? I'd rather a phone that was powered by my own farts. (Can you imagine an amorous conversation on that on

Yes, taking it to an stupid extreme for stupid people makes this seem like a stupid idea.

The sound waves produced a mild electrical current of about 50 millivolts. The article recognizes the fact that the current state of this technology would not charge cell phones. I suspect it won't work that way;however there are many other used.

Like putting it along walls near freeways and using it to charge a battery that powers LED overhead traffic lights. Because you would have about 30 meters by 3 meters are to use

The phone already taps the energy of sound, if their was no energy in the sound then the microphone would not be able to pick up the sound waves and send the information on.

But even assuming that they can get the device to convert the power to small enough it does not matter, you would need a wide receiver, as the energy dissipates in all directions at a squared rate.and I would think that even if you converted all the power it would still not even be close to enough.think about it, you are basically saying the energy taken from a person speaking normally could be used for the same voice to be heard miles away, does not sound like it follows the laws of conservation of energy unless you think that it will be operating at 100% efficiency.

They are saying they have a device that they can get 50mw at 100db, and the expect refinement to make it better.

That said, people should stop focus on cell phones and look at a bigger picture. Like walls along the sides of freeways.Yes, the used cell phones as a way of grabbing attention, but educated people should realize that's all it is and focus on actual practical implication.

think about it, you are basically saying the energy taken from a person speaking normally could be used for the same voice to be heard miles away, does not sound like it follows the laws of conservation of energy unless you think that it will be operating at 100% efficiency.

When I was about 11, a friend and I made a "phone network" between our houses. We used two earpieces taken from old rotary phones, and simply connected them to each other using common 2-core speaker wire. This was over a distance of about 300meters, and used NO external power. You simply spoke into one earpiece, and the sound was heard at the other end. so we basically had a permanent open channel between our bedrooms.

When we wanted to "call" the other person, we simply held an alarm clock next to the earpi

From TFA - "Just as speakers transform electric signals into sound, the opposite process -- of turning sound into a source of electrical power -- is possible"

I never would have guessed that. Maybe now they can make something capable of turning sound into electrical impulses. I will patent that idea I think - and call it an anti-speaker. Or an audioelectictransmogrifier for short.

While we're quoting the article - this rather tickled me. Particularly strange when it's taken out of context, but nicely indicative of the sort of language you get in tech articles trying to cater to laymen:

"The researchers blasted that sandwich with sound waves, which at 100 decibels were not quite as loud as a rock concert."

The sound waves produced a mild electrical current of about 50 millivolts. The average cell phone requires a few volts to operate, several times the power this technology can currently produce.

Wrong, so very wrong. Millivolts is not a unit of current, and volts is no unit of power. Nor is power current. I've seen journalists not understanding electrical units before, but never have I seen something quite so wrong as this.

Shhhh. Your going to confuse average joe-sixpack even more. The editors must have assumed that their tripe would pass the standard jargon filter. Does anybody have a regex for finding all the jargon in some text, so you can subsequently replace it with stuff this guys says? [youtube.com]

"A patent for a mobile telephony network requiring no power. Telephone A, consisting of a hollow cylindrical object with a hole drilled into the bottom, is connected via a high tech, string-like device, to Telephone B, another cylindrical object with the hole cut in the bottom. Range is excellent provided you buy lots of Monster brand string, it can even reach my super-secret treehouse!"

"The sound waves produced a mild electrical current of about 50 millivolts. The average cell phone requires a few volts to operate, several times the power this technology can currently produce....The Korean scientists agree: 50 millivolts is not a lot of power, but they also say their research is proof of concept. As they continue their work, they expect to get a higher power output."

Scientists from Korea have turned the main ingredient of calamine lotion into a tiny material that converts sound waves into electricity.

"Just as speakers transform electric signals into sound, the opposite process -- of turning sound into a source of electrical power -- is possible,"

Wow, somebody has to tell these Korean scientists that they are 134 years late in discovering the microphone. Perhaps they should work on the next big problem Korea is facing : Fan deaths [wikipedia.org]...

PS. I hope talking about measuring power & current with volts is the journalists fault.

I've been experimenting with this for quite some time now, using off-the-shelf parts from Linear Technologies [linear.com], specialty micro transformers from Coilcraft, and standard junkbox parts. Both companies offer free samples, but the chips and associated coils are each under $5 each anyway.

I found the LTC3108 [linear.com] (or the LTC3801-1 variant) best suited most of my projects, but the LTC3588/LTC3588-1 [linear.com] is better for capturing energy from ambient sound or vibration via a piezoelectric transducer. (Their evaluation kit, wh

There's a big difference between using people's weight to make electricity (whether by piezoelectrics, or simpler physics of gravity and moving parts) and doing so by the force of exhaled breath touching an area some distance away.

And what you miss is that these people are *also*, somehow, using their own energy to power the lights. It's no different to having a pedal-powered bike to power the lights - the effort is just spread across a lot of people. Those people still needed to use the energy, so it was